The present invention relates to a method of operating a metering or dispensing apparatus for transferring accurately determined volumes of liquid from vessels containing said liquids to other vessels, for example to reactor tubes forming part of an automatic clinical analysis apparatus. The metering apparatus to which the invention refers is of the kind which comprises a metering pump having a pump cylinder which tapers to a point at one end and in which a filling orifice is located at the pointed end of said cylinder. A piston is arranged for axial movement in the pump cylinder and seals against the internal wall surface thereof. The piston has a maximum terminal position of forward displacement at said cylinder end, and when occupying this forward terminal position, the cylinder volume communicating with the filling orifice in said pointed end of the cylinder is O. The apparatus is provided with means for accurately controlling the axial movement of the piston in the cylinder, so that the cylinder volume communicating with said filling orifice can be suitably varied. The apparatus is also provided with means for moving the pump horizontally and vertically. An advantageous embodiment of a metering apparatus of the aforedescribed kind is described, for example, in the European Pat. No. 009013 issued June 2, 1982 (corresponding to U.S. Pat. No. 4298575 issued Nov. 3, 1981). This known metering apparatus is a high precision apparatus in which, for example, the piston can be moved through extremely accurately determined distances within the pump cylinder, and in which when the piston is moved to its maximum forward terminal position in the cylinder, the pointed end of the cylinder is completely filled by the piston, such that no residual volume remains within said cylinder. Despite the attributes of this known apparatus, however, considerable difficulty is experienced in obtaining the desired high degree of accuracy with respect to the volumes of liquid transferred by said apparatus, and primarily in preventing the carry-over of one liquid to another liquid when the metering apparatus is used for transferring given volumes of several different liquids sequentially, and the carry-over of washing liquid, normally distilled water, which is used for washing the interior of the pump cylinder between the transfer of two mutually different liquids. It will be understood that such carry-over must be avoided, since it results in contamination and dilution of the liquids transferred. These problems are related to the fact that even with the most accurate of metering apparatus of the kind described it is difficult to completely eliminate resilience and play in the system which drives the piston in the pump cylinder. Further, in order to be able to dispense accurately determined volumes of liquid, it is necessary to obtain a well defined and stable jet of liquid from the pointed end of the cylinder throughout the whole of a dispensing operation, said jet being initiated and interrupted practically instantaneously. If the liquid jet is not well defined and stable, the jet is liable to break up and cause splashing at the beginning and the end of a dispensing operation. Further, liquid is liable to wet the outer surface of the pointed end of the pump cylinder or form a droplet on said end.